In the “RuhBio” research project, scientists at Hof University of Applied Sciences are working together with industrial partners to develop innovative nonwoven materials for rail transportation. The goal is ambitious: Conventional soundproofing elements, such as those currently used in trains, are to be replaced by a sustainable, bio-based alternative. The team is supported by the companies Cellofoam GmbH, ROWA F. Rothmund GmbH & Co. KG and the Thuringian Institute for Textile and Plastics Research (TITK). The research work began at the start of 2023 and will be completed by the end of this year. The project is being funded by the Federal Ministry for Economic Affairs and Climate Protection as part of the Central Innovation Program for SMEs (ZIM).
Until now, noise protection components in rail transportation have mostly been made of conventional foams or polyester fleeces.
Although functionally proven, these materials are neither bio-based nor biodegradable.”
Robin Heinrich, research associate at the ibp
Circular Economy of Bio:Polymers at Hof University of Applied Sciences (ibp);
Image: Hof University of Applied Sciences;
In order to meet the growing environmental awareness and sustainability goals in the transport sector, the project team at Hof University of Applied Sciences is focusing on polylactide, or PLA for short – a bioplastic made from renewable raw materials such as corn starch. PLA is already used in numerous applications, such as packaging or medical products. However, the focus there is usually on biodegradability, not long-term durability.
New requirements for a familiar material
Different standards apply for use in rail transportation. Materials must remain stable over many decades and withstand extreme environmental conditions. Temperatures between minus 40 and plus 100 degrees Celsius and high humidity are not uncommon. The “RuhBio” project therefore sets two central development goals: On the one hand, the temperature resistance of the PLA material must be significantly increased, and on the other hand, hydrolytic degradation, i.e. decomposition due to moisture, must be reliably prevented.
Image: Hof University of Applied Sciences;
High-tech from two components
The solution lies in a newly developed fiber structure: a so-called bicomponent fiber with a core-sheath structure combines the desired properties. The core consists of a semi-crystalline PLA type with talc content and gives the material the necessary heat resistance and mechanical stability.
The sheath, in turn, consists of amorphous PLA with a wax content. This combination makes the nonwoven material resistant to moisture and at the same time enables it to be thermally bonded.
Caffeine against material degradation
A particularly innovative approach is the addition of caffeine as a biogenic residue. This is obtained from coffee residues and helps to further inhibit hydrolytic degradation. A special hydrolysis test was developed in order to be able to assess the material quality in the long term. Samples of the new material are stored in water at 50 degrees Celsius for up to ten weeks. Before and after storage and after a drying phase, they are weighed, examined microscopically and tested for their mechanical properties.
From the lab to the train
The material mixtures developed were initially processed on a laboratory scale. After successful optimization, however, larger quantities of fibres could now be produced, which the project partner ROWA processed into nonwovens. Finally, Cellofoam GmbH takes over the packaging and lamination and uses them to produce ready-to-install soundproofing elements for real-life use.
A contribution to the mobility of tomorrow
With the “RuhBio” project, Hof University of Applied Sciences impressively demonstrates how application-oriented research, ecological responsibility and technological innovation can go hand in hand. The result is a future-oriented material that meets the high demands of rail transportation and at the same time sets new standards in terms of sustainability. In this way, the project not only contributes to further technical development, but also to environmentally friendly mobility in the future.
